The present invention relates to an apparatus for supporting an elongate member. More particularly, this invention concerns a balanced snubber apparatus for suppression of longitudinal shock in a pipe, conduit or the like without inducement of bending forces.
The proper mounting and support of pipes conveying fluids involves several problems. Both static and dynamic loads must be equalized. The static load comprises primarily the weight of the pipe and the weight of the fluid carried therein. The dynamic load typically comprises the forces produced by movement of the fluid, together with any vibration caused by machinery. In addition, allowance must be made for temperature expansion of the pipe. Pipes conveying heated fluids are thus supported semi-rigidly to allow some movement.
In some situations the possibility of shock or impulse loads must also be taken into account in the design of pipe supports. For example, consider the extensive and large-scale piping systems utilized in a power plant. In some geographical areas, it is necessary to provide for shock suppression to the pipe in the event of an earthquake, earth tremor, blast or other emergency. Provision for pipe shock suppression is especially critical in a nuclear power plant. The pipes must be supported in a way permitting some movement, while not allowing the destructive type of movement otherwise caused by shock to a semi-rigidly supported structure.
Suppression of shock in the axial direction of a pipe is especially difficult to achieve without interfering with the natural movement of the pipe and without causing undesirable reaction forces in the pipe. The prior art approaches to this problem include using pairs of parallel snubbers or shock absorbers, one snubber being located on each side of the pipe. If only one snubber is located parallel to the pipe, the snubber force reaction to a shock induces differential bending in the pipe. Two snubbers located on opposite sides of the pipe minimize the bending moment induced, but only if the snubbers are cross-coupled or precisely matched in performance. Matching of snubber performance is not reliable on a long term basis, while cross-coupling of parallel snubbers reduces reliability and requires additional maintenance. There is thus a need for an improved snubber support for longitudinally suppressing the shock in a pipe without effecting a bending moment in the pipe.
The present invention comprises a balanced snubber device to overcome the foregoing and other problems associated with the prior art. In accordance with the broader aspects of the invention, a walking beam structure is secured to a pipe. The walking beam structure is pivoted about an axis extending through the centerline of the pipe. Two support members are pivotally connected to the walking beam structure on opposite sides of the pipe so that longitudinal loads to the pipe are reacted without causing a bending moment therein. The invention permits natural axial movement of the pipe but anchors the pipe in place upon a shock to minimize damage. Only one conventional snubber is employed in the present invention, thereby eliminating the problems of snubber matching or cross-coupling characteristic of the dual snubber devices of the prior art. Use of the snubber device of the present invention reduces maintenance expense and enhances reliability.
In accordance with more specific aspects of the invention, a balanced snubber device for axially supporting a pipe or conduit includes a walking beam assembly having an inner portion pivotally mounted within an outer portion. The inner portion of the walking beam assembly is adapted to be clampingly secured to the pipe, and preferably between upper and lower sets of shear lugs on the pipe. The axis of the pivotal connection between the inner and outer portions of the walking beam assembly extends through the centerline of the pipe. Two parallel support members are coupled between a suitable base and the outer portion of the walking beam in opposing relationship. The support members are coupled to the walking beam assembly at points displaced from the pivotal connection between the inner and outer portions of the assembly. One support member comprises a rigid link. The other support member comprises a conventional snubber or shock absorber. The snubber permits ordinary, expected longitudinal displacement of the pipe, but locks in the event of an unexpected sudden shock force to stabilize the pipe. All reaction forces by the balanced snubber apparatus of the present invention are directed through the centerline of the pipe so that no bending moments are induced in the pipe.